The present invention relates to a device for injection moulding plastic parts by the fusible core technique.
Nowadays it is well known to have recourse to the injection-moulding technique called fusible core technique in order to produce hollow parts of complicated profile. This technique, which is described especially in patent FR-A-1,162,096, involves at least four principal successive steps:
moulding a fusible core by low-pressure injection of a low melting-point metal into a metal mould;
injection moulding the desired part by injection of a plastic by using a conventional injection press whose mould is furnished beforehand with a fusible core;
extracting the fusible core embedded in the moulded part, by melting and recovering the metal, after extracting the part from its injection mould;
washing the moulded part stripped of the fusible core.
These successive operational steps require recourse to a series of suitable units, namely units for moulding the fusible core, for injection moulding the part, for melting and recovering the fusible core and for washing the part, and they imply, consequently, a series of transfers either of the fusible core or of the moulded part between these various units. Taking into account, furthermore, the fact that for many applications the weight of the fusible core can vary between 10 and 50 kg, it seems desirable to be able to automate all the necessary operational steps by means of a moulding cycle.
For this purpose, it is possible certainly to envisage using a robot to carry out some of these operational steps, but it turns out that such a means cannot provide all the numerous operational steps required during a moulding cycle--taking hold of and extracting the moulded part, transferring this part into the unit for melting the fusible core and then into the washing unit, taking hold of and extracting a fusible core from its moulding unit, positioning and leaving this fusible core in the injection press--whilst permitting an acceptable productivity. In particular, by proceeding in this logical order, it appears that the injection press is inactive during the cycle of successive transfers of the part moulded during the previous cycle.